1. Field of the Invention
The present invention relates to a method of manufacturing a fatty acid ester of polyoxyalkylene alkyl ether having an alkylene oxide in an extremely narrow molar distribution, by directly reacting an fatty acid alkyl ester with an alkylene oxide using a surface-modified composite metal-oxide catalyst.
2. Description of the Related Art
Fatty acid esters of polyoxyalkylene alkyl ethers are known as ester-type nonionic surfactants. Of these, stearic polyoxyethylene stearyl ether represented by the following formula (1) is utilized as an emulsifier, a dispersant, or an oil-phase adjuster in the cosmetics field and in various industrial fields. ##STR2##
Polyoxyethylene methyl ether laurate represented by the following formula (2) has been investigated as to the possibility for use in a wetting agent (JAOCS, 56:873 (1979)). ##STR3##
Application of the fatty acid esters of polyoxyalkylene alkyl ethers to detergent compositions (Jpn. Pat. Appln. Nos. 3-229548, 3-321106), to deinking agents for use in a paper regeneration process (Jpn. Pat. Appln. No. 4-209010), or to others have been also expected.
A polyoxyethylene alkyl ether and a polyoxyethylene fatty acid ester, each to be used as a typical nonionic surfactant of an ethylene oxide adduct type, can be obtained by using an alcohol or a fatty acid as a starting material, and directly addition-polymerizing ethylene oxide and the staring material in the presence of an alkaline or an acidic catalyst.
In the case of obtaining a fatty acid ester of polyoxyalkylene alkyl ether, however, the addition polymerization reaction of an alkylene oxide does not proceed even if a fatty acid alkyl ester is allowed to react with an alkylene oxide in the presence of an alkaline or an acidic catalyst.
The methods of manufacturing a fatty acid ester of polyoxyalkylene alkyl ether by means of a one-step reaction between a fatty acid alkyl ester and an alkylene oxide are reported in the following publications:
1) Jpn. Pat. Appln. KOKAI Publication No. 56-36431: acetic acid ester of polyoxyalkylene alkyl ether is synthesized from an alkyl acetate and an alkylene oxide, using a calcined hydrotalcite compound as a catalyst.
2) Jpn. Pat. Appln. KOKOKU Publication No. 53-24930: a fatty acid ester of polyoxyalkylene alkyl ether is produced through a reaction between an alkylene oxide and an organic carboxylate by using a catalyst consisting of a halide of zinc, aluminum or the like, or consisting of an organometallic compound containing zinc or aluminum, or by using an alternative catalyst consisting of a combination of the aforementioned catalyst and an amine compound or the like.
3) Jpn. Pat. Appln. KOKAI Publication No. 54-1038125: acetic acid ester of polyoxyethylene ethyl ether is produced through a reaction between ethyl acetate and an excessive ethylene glycol monoethyl ether in the presence of a strong acidic cation exchange resin.
4) Jpn. Pat. Appln. KOKAI Publication No. 4-279552: a fatty acid ester of polyoxyalkylene alkyl ether is synthesized by means of a reaction between a fatty acid alkyl ester and an alkylene oxide, using a metal-ion (aluminum etc.) added magnesium oxide as a catalyst.
5) Jpn. Pat. Appln. KOKAI Publication No. 4-505449: a fatty acid ester is ethoxylated or propoxylated by using a calcined hydrotalcite as a catalyst.
As mentioned above, when a fatty acid alkyl ester is reacted with an alkylene oxide in the presence of a composite metal-oxide catalyst such as a metal-ion (aluminum etc.) added magnesium oxide or a calcined hydrotalcite, it is known that the alkylene oxide is added to the fatty acid alkyl ester in such a way that the alkylene oxide enters into an ester bond, resulting in a fatty acid ester of polyoxyalkylene alkyl ether.
The aforementioned methods are, however, not fully satisfactory from an industrial point of view due to three drawbacks. First, an alkylene oxide adduct distribution in a product is wide. Second, an unreactive fatty acid alkyl ester is remained in a large amount. Third, the product is colored.